1. Field of the Invention
The present invention relates to a new phosphine transition metal complex, a method for producing the same, and an antitumor agent containing the same.
2. Description of the Related Art
Platinum complexes such as cisplatin (cis-dichlorodiamine platinum (II)), carboplatin (cis-1,1-cyclobutanedicarboxylate diamine platinum (II)), and nedaplatin (cis-O,O′-glycolate diamine platinum (II)) have high antitumor activity and are used as principal antitumor agents.
PCT Japanese Translation Patent Publication No. 10-509957 discloses phosphine transition metal complexes expressed by general formula (4):

wherein R1′ to R8′ may be the same or different and each represent phenyl, substituted phenyl, or pyridyl; A′ represents linear alkylene or cis-vinylene; M′ represents gold, silver, or copper; and B′ represents an anion species. Japanese Unexamined Patent Application Publication No. 61-10594 also discloses phosphine transition metal complexes expressed by the same general formula (4), wherein R1′ to R8′ all represent the same phenyl, substituted phenyl, or ethyl, or R1′, R2′, R7′ and R8′ represent phenyl while R3′ to R6′ represent ethyl; A represents a linear alkylene or cis-vinylene; M′ represents gold, silver, or copper; and B′ represents an anionic species. It is known that these phosphine transition metal complexes have antitumor activity comparable to that of cisplatin.
In general, however, the antitumor activity and antitumor spectrum of a compound heavily depend on the chemical structure, and a small change in the structure results in a large difference in characteristics. In addition, the efficacy of an antitumor agent varies depending on the person. For example, even taxol, which is considered to be the most effective antitumor agent, exhibits an effectiveness of at most about 30%. It is desired that a variety of new antitumor agents having different structures are developed.